Carrier frequency communication system



CARRIER FREQUENCY COMMUNICATION $Y$TEM arch 1%,

Filed Aug. 4,1938 2 Sheets-Sheet 1 flanvl rfi'ezumcy l/zpuf 7 Telephone Lmea z I E 5 I OLHTW Z Lon/Pass fi/fers\ \7. I i I;-

: I 1 E I) E21 14 22 HU /m/ an for Alfred M'essngr Patented Mar. 18, 1941 PATENT OFFICE CARRIER FREQUENCY COMMUNICATION SYSTEM Alfred Wiessner, Berlin, Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany, a company Application August 4, In Germany 2 Claims.

The present invention relates to carrier frequency communication systems, and more specifically to arrangements in telephone systems effecting wired radio frequency message transmission.

The incoming lines to telephone exchanges are generally terminated in a so-called main distributor which customarily consists of a plurality of terminal strip assemblies in which the telephone lines are-wired with the exchange equipment, such as selectors, for example.

In case that the telephone lines are utilized for various purposes, e. g. wired-radio, alarms and the like, by carrier frequency transmission, electric separating filters must be interposed in the lines utilized for a varietyof purposes. Such filter devices may be arranged as additional circuit ele ments inparticular racks or frames of the exchange equipment, but this arrangement suffers 20 under the disadvantage of a considerable expenditure with respect to wiring connections since the low-pass filters which have for their objects to prevent high-frequency interfering voltages from obtaining access to the exchange equipment must be inserted in the appertaining telephone line. For this reason endeavor has beenmade to arrange the filter devices in the main distributor itself since this expedient does not require additional wiring connections when interposing the low-pass filters in the telephone lines.

In addition to the interposition of the low-pass filters in the telephone lines serving various purposes, the carrier frequency line must be connected through high-pass filters and this is generally accomplished likewise in the main distributor. Numerous problems call for the attention of the experts when the possibilities of arranging the filters in the main distributor are to be considered, and these problems are by no means restricted to problems of construction since certain conditions must be taken in account which are of great importance for securing relevant operation. It is the main object of the present invention to provide means which enable a simple solution of all such problems.

An improvement with respect to the overall functioning of the arrangement is involved if the low-frequency path is interruptable in a sim- 0 ple manner without simultaneously interrupting the high-frequency transmission. Moreover, the possibility of securing a low-frequency separation is of great importance when a subscribers line is to be blocked or interrupted when the location of a trouble is to be ascertained. It is, on the 1938, Serial No. 223,019 August 4, 1937 other hand, desirable that the high-frequency supply may be individually cut off for each line when it is required to determine interferences or troubles in the high-frequency path, or during the level regulation of the high-frequency supply. 5 It is then of great importance that the aforesaid operations do not simultaneously cause the interruption of the low-frequency path since this latter would mean an interruption of the telephone connection.

The aforesaid considerations have been taken in account in the present invention and have been efiected according to the invention by c0nstructively and physically separating the lowpass and the high-pass elements of the filtering 15l devices in such a manner that the number of necessary contacts is not increased over the numberwhich is required when the low-pass and the high-pass elements are assembled to one unit.

The high-frequency message current is, as heretofore proposed, applied to the main distributor of such telephone exchange, and the terminal strip assemblies provided in this main distributor are so designed that a minimum of additional interconnecting leads is required for applying the high-frequency current and, moreover, that neither the high-frequency path becomes interrupted in cases'when the low-frequency is cut oil nor that the low-frequency path is interrupted when the high-frequency is disconnected.

The invention will be more readily understood from the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 schematically illustrates a wiring diagram according to the invention; Fig. 2 is a cross section through a terminal strip assembly according to one feature of the invention; Fig. 3 is the side elevation of the arrangement shown in Fig. 2; Fig. 4 represents a further embodiment as a modification of the arrangement shown in Fig. 2; while Fig. 5 shows a modification over the arrangement as disclosed in Fig. 1'.

Referring to Fig. 1, the cores of the telephone lines are connected to the terminal strip assembly the soldering tabs of which are denoted I. The terminal strip assemblies are located in the main distributor. Further soldering tabs 2 like wise fixed in the terminal strip assembly serve for establishing connections to the selector devices forming part of the exchange equipment. The low-pass filter 3 which has for its object to block the telephone line against high-frequency interference voltages set up at the contacts of the selector or exchange equipment and to protect the selector equipment against high-frequency oscillations which are impressed upon the telephone line, is interposed between said soldering tabs l and 2.

The aforementioned low-pass filter which, for instance, may be designed as a so-called 1r-circuit comprises two inductances 5 and 6 connected in series with the line and shunted by two condensers l and 8 in serial relation to one another. The mid-point between these condensers may be earthed at E. High-frequency oscillations are applied through condensers 9 and [0 which simultaneously constitute one shunt capacity member of the low-pass filter since these condensers are likewise bridged between the lines. The high-frequency oscillations reach these coupling condensers over suitable tapping points of a transformer H.

The above described circuit arrangement according to Fig. 1 is placed in a box and the appropriate number of such boxes is arranged in a terminal strip assembly shown in the Figs. 2 and 3 which, for example, is adapted to receive twenty such box devices. The terminal strip assembly l2 in the Figs. 2 and 3 comprises a box-shaped casing at the upper edge of which pairs of soldering tabs are arranged in a row or rows in which the subscribers lines are terminated. At the opposite end of the terminal strip box further 20 pairs of soldering tabs are fixed in a row or rows to which the connecting leads to the selector equipment are connected. The low-pass filters schematically indicated in Fig. 1 may be placed in the interior of the box-shaped housing so as to form four tiers each of which consists of five filter elements so that the same number of filters is provided as telephone lines are terminated in the terminal strip assembly. Each low-pass filter device is mounted in a small box l3 which carries at one end a number of connector plugs with which the filter elements are connected. These connector plugs may be inserted in corresponding connector sockets I4 fixed in said housing so as to interpose the filter element in the appertaining telephone line. The condensers 9 and ID, on the other hand, are mounted together in the configuration of a small plug shown at 15 in Fig. 3, or at IS in Fig. 4. These plug-shaped condensers are insertable in corresponding apertures or openings which are arranged in the terminal strip housing. Each plug-shaped condenser member l5 carries suitable contact surfaces, e. g. at its outer circumference, and these contact members are adapted to establish electric connection with appropriate contact surfaces arranged in the interior of the aperture or opening receiving said condenser member l5. The last mentioned contact surfaces are connected individually to a number of tapping points of the secondary winding of the transformer H indicated in Fig. 2 and Fig. 1. It is thus possible by adjusting or interchanging the member I5 to select the necessary voltage for transmission.

The interruption of the low-frequency line or lines is thus accomplished in a very simple manner by removing one of said low-pass filter boxes 13 without disconnecting the high-frequency supply impressed through the transformer II and the condenser member l5. Telephone lines which are not utilized for more than one purpose neither require a low-pass not a high-pass filter, so that a short-circuiting plug device is adapted to substitute the low-pass filter allotted to such lines.

Fig. 5 shows a further possibility of carrying out the invention. The low-pass filter comprises a filter member which is designed as a so-called H-circuit and the high-frequency oscillations are applied through a high-frequency transformer I I in which a condenser is included so as to interrupt a direct current path.

What is claimed is:

1. In a telephone system means for interconnecting a plurality of subscriber lines for communication by carrier frequency currents and Voice frequency currents comprising, a terminal strip comprising a subscriber line connecting tabs, exchange equipment tabs, and carrier input means. permanently mounted on said terminal strip, removable high pass filter means and low pass filter means mounted on said terminal strip to interconnect respectively said carrier input means and said subscriber line, and said exchange equipment tabs and said subscriber line, and mean holding said permanently mounted elements all in fixed relation and provided with connections whereby insertion of said high pass filter will complete a circuit for said carrier frequency to said subscriber line, and insertion of said low pass filter will complete a connection for said exchange tabs to said subscriber line.

2. A telephone system according to claim 1, wherein said carrier input means comprises a transformer having a primary winding and a secondary winding, said secondary Winding having a plurality of separate taps arranged for individual contact, and wherein said high pass filter means comprises a pair of condensers mounted in a unit having means for connecting said condensers selectively with separate taps on said secondary winding and with said subscriber line tabs.

ALFRED WIESSNER. 

